1. Field of the Invention
The present invention relates to composite particles for electrodes and electrochemical devices.
2. Related Background Art
Lithium-ion secondary batteries with improved discharge capacities and rate characteristics requires enhanced ion diffusion capabilities of active materials used for electrodes of the secondary batteries, increased contact areas between the active materials and electrolytic solutions, or enhanced electron conductivities of active materials. Methods for enhancing the ion diffusion capability of the active material and increasing the contact area between the active material and the electrolytic solution include reduction in particle size of the active material. Methods for imparting electron conductivity to the active material include compounding of the active material with an electron-conducting material such as carbon.
Such a composite of the active material and carbon includes a carbonaceous composite of lithium-iron-phosphorous-based complex oxide, which is composed of particulate LiFePO4 coated with the conductive carbonaceous material, the particulate LiFePO4 being made from ferrous phosphate octahydrate (Fe3(PO4)2.8H2O) and lithium phosphate (Li3PO4), the carbonaceous composite being characterized by having an average particle size of 0.5 μm or less, as is disclosed in Japanese Patent Application Laid-open No. 2003-292308, for example.